AR Display Optical Arrangement for Expanded Field of View
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Solution Overview
Problem
Augmented reality (AR) devices have a limited field of view due to the mechanisms used for combining virtual and physical imagery, resulting in 'artificial windowing' and 'framing' effects that disrupt immersion, with existing technologies like fold optics and waveguide image combiners offering limited acceptance angles and requiring more space for optimal viewing.
Innovation Solution
An optical arrangement featuring an off-axis, short-throw projector and a substantially transparent projection screen within the field of view, directing imagery toward a reflective element to increase the field of view without the need for fold optics, allowing the viewer's eyes to be positioned closer to the reflective element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fold optics are used to combine virtual and physical imagery, then the device can provide a combined view, but the device requires more space and increases the distance from the viewer's eye to the imaging eyepiece, which reduces the field of view
Solution Approach 1:
The patent transitions from a folded optical path (requiring multiple reflections and more space) to a more direct optical path arrangement. By positioning the imaging eyepiece closer to the viewer's eye and using a different optical combination approach, the system achieves a larger field of view without relying on traditional fold optics that consume space and reduce the subtended angle.
2Area of moving object
If waveguide image combiners are used to position the imaging eyepiece closer to the viewer's eye, then the field of view increases, but the acceptance angle is limited due to total internal refraction
Solution Approach 1:
The patent introduces a beam combiner as an intermediary element that merges the virtual image path with the real world view path. This beam combiner allows light from both sources to be combined effectively, enabling the imaging eyepiece to be positioned closer to the viewer's eye while maintaining a wide acceptance angle that overcomes the limitations of waveguide-based total internal refraction.
3Device complexity
If the imaging eyepiece is positioned further from the viewer's eye, then fold optics can be used, but the subtended angle decreases and the field of view becomes smaller
Solution Approach 1:
The patent reconfigures the optical arrangement to position the imaging eyepiece in a different spatial relationship to the viewer's eye, achieving a larger subtended angle. By using a beam combiner and adjusting the optical path geometry, the system eliminates the need to position the eyepiece far away, thereby increasing the field of view while maintaining a compact form factor.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the field of view, providing a more immersive experience by reducing 'artificial windowing' effects and allowing for a seamless combination of virtual and real worlds, while also making the AR device more compact and aesthetically pleasing.
Implementation Method 1
because waveguide image combiners operate using the principle of total internal refraction (TIR), the acceptance angle, and thus the field of view, is limited
Implementation Method 2
a reflective element arranged within the field of view... after direction by the reflective element, transmit the imagery toward the optical reference point
Data Source
AI summary
Aspects described herein include an optical arrangement that defines a field of view relative to an optical reference point. The optical arrangement comprises a reflective element arranged within the field of view, an off-axis, short-throw projector arranged outside the field of view, and a substantially transparent projection screen arranged within the field of view. The projection screen is configured to preferentially direct imagery projected by the off-axis, short-throw projector toward the reflective element, and to, after direction by the reflective element, transmit the imagery toward the optical reference point.